This invention relates to hydraulic clutch actuation systems and more particularly to hydraulic systems employing a damper mechanism.
Hydraulic actuation systems are known for operating a mechanism at a remote location by way of a master cylinder connected to a slave cylinder installed at a remote location. A conduit interconnects the master cylinder to the slave cylinder and the hydraulic apparatus is filled with hydraulic fluid such that, when the piston of the master cylinder is actuated the piston of the slave cylinder and consequently the piston rod or output member is simultaneously actuated by displacement of the hydraulic fluid from the master cylinder to the slave cylinder through the conduit.
More particularly, it is known to provide such a system for operating the clutch of a motor vehicle so that when the clutch pedal of the vehicle is depressed by the driver, the slave cylinder is actuated to operate the clutch in known manner. Whereas hydraulic clutch actuators have enjoyed significant commercial success they have the ability to transmit vibrations backwardly through the system from the clutch to the clutch pedal with the result that the operator may experience unpleasant vibrations at the clutch pedal.
Specifically, imbalances in the crankshaft of the vehicle engine or engine firing impulses are transmitted to the flywheel which undergoes a swashing movement, the flywheel swashing movement in turn leads to vibrations of the spring fingers of the clutch release mechanism, the vibrations of the spring fingers are transferred to the release bearing of the clutch, and the vibrations propagate backwardly through the hydraulic fluid in the slave cylinder, through the hydraulic fluid in the conduit interconnecting the slave cylinder and the master cylinder, through the hydraulic fluid in the master cylinder, and thence through the master cylinder push rod to the clutch pedal where they are experienced by the operator as vibrations of the clutch pedal. The propagated vibrations also generate fire wall buzz and pedal growl which is audible to the operator as well as a clutch roar which may also be audible to the operator.
Various devices have been proposed in an attempt to attenuate these vibrations. For example, tuned masses have been attached to various parts of the clutch system including the clutch release lever, the slave cylinder push rod, and the clutch pedal. Rubber dampers have also been employed in the master cylinder push rod, rubber hose sections have been employed in the conduit interconnecting the master cylinder and the slave cylinder, and various damper devices have been proposed for installation in the interconnecting conduit.
Whereas these prior art devices have been successful in varying degrees in attenuating the vibrations in the system, they have each suffered one or more shortcomings. Specifically, the prior art devices have been unduly expensive; or they have actually introduced vibrations into the system by virtue of a hysteresis effect; or they have required a package size that has complicated their installation and placement in the crowded under hood environment of a modern day motor vehicle; or they have been difficult to selectively adjust to accommodate varying vehicular applications.